Characterizations of inner product structures involving the radius of the inscribed or circumscribed circumference

summary:We define the radius of the inscribed and circumscribed circumferences in a triangle located in a real normed space and we obtain new characterizations of inner product spaces

Spatial and temporal distribution of marine debris in seafloor habitats of the Balearic Islands

The weight and distribution of marine macrodebris in benthic habitats (continental shelves and upper slopes) from bottom trawl scientific surveys at the Balearic Islands was investigated. A time series of 15 years (2001 -2015) was studied at mesoscale level. Most abundant debris were glass, plastic and fishing material. The plastic fraction, which is highly persistent and resistant to biodegradation, showed a high variability in space and time with no clear trend

Exploring the Photocyclization Pathways of Styrylthiophenes in the Synthesis of Thiahelicenes: When the Theory and Experiment Meet

The introduction of thiophene rings to the helical structure of carbohelicenes has electronic effects that may be used advantageously in organic electronics. The performance of these devices is highly dependent on the sulfur atom topology, so a precise knowledge of the synthetic routes that may afford isomeric structures is necessary. We have studied the photocyclization pathway of both 2- and 3-styrylthiophenes on their way to thiahelicenes by experiment and theory. To begin with, the synthesis of stereochemically well-defined 2- and 3-styrylthiophenes allowed us to register first, and simulate later, the UV–vis electronic spectra of these precursors. This information gave us access through time-dependent density functional theory calculations to the very nature of the excited states involved in the photocyclization step and from there to the regio- and stereochemical outcome of the reaction. For the widely known case of a 2-styrylthiophene derivative, the expected naphtho[2,1-b]thiophene type of ring fusion was predicted and experimentally observed by synthesis. On the contrary, 3-styrylthiophene derivatives have been seldom used in synthetic photocyclizations. Among the two possible structural outcomes, only the naphtho[1,2-b]thiophene type of ring fusion was found to be mechanistically sound, and this was actually the only compound observed by synthesis.Financial support by the Spanish Ministerio de Economía y Competitividad (MAT2016-78625-C2-2-P), the Ministerio de Ciencia, Innovación y Universidades (PID2019-109539GB-C4 and PGC2018-096955-B-C44), the Generalitat Valenciana (PROMETEO/2017/139), and finally, the University of Alicante (VIGROB-285) is gratefully acknowledged. The computational resources provided by the Department of Applied Physics of the University of Alicante are greatly appreciated

Electrochemically site-selective alkoxylation of twisted 2-arylbenzoic acids via spirolactonization

The Electrochemical Cross-Dehydrogenative Coupling (ECDC) of twisted biphenyl-2-carboxylic acids with aliphatic alcohols provides 4′-alkoxyspirolactones which isomerize, under mild basic conditions, to give 4′-alkoxy-2-phenylbenzoic acids. This site-selective alkoxylation was readily adapted to 1 mmol scale and is environmentally friendly, as no terminal oxidants are needed and H2 is the only residue. The suitability of diphenic acid derivatives in this two-step protocol is noteworthy, especially for axially chiral substrates that can be functionalized with retention of the configuration and of the enantiomeric purity. We have proposed a plausible mechanism based on experimental pieces of evidence that support the single-electron oxidation of the carboxylate, formed by deprotonation of the biphenyl-2-carboxylic acids with 2,6-lutidine, and DFT calculations that suggest a very fast spirocyclization of the intermediate σ-aroyloxyl radical. Competing pathways to benzocoumarins were also examined by computational studies.This work was generously supported by the Spanish Ministerio de Ciencia, Innovación y Universidades (MICIU; grant no. CTQ2017-88171-P) and the University of Alicante (grant no. VIGROB-285/19). I. B. acknowledges the Spanish MICIU for a Juan de la Cierva-incorporación grant (no. IJCI-2017-33706)

Synthesis of Propargylamines by Cross-Dehydrogenative Coupling

Propargylamines are versatile compounds for heterocyclic synthesis, some of which are current drugs prescribed to treat patients with Parkinson’s disease. There are different methods to synthesize propargylamines, however, modern chemistry has moved progressively to rely on new strategies that meet the principles of Green Chemistry. In this context, propargylamines are readily accessible by the cross-dehydrogenative coupling (CDC) of two C-H bonds (i.e., NCsp3-H and Csp-H bonds); surely, CDC can be considered the most atom-economic and efficient manner to form C-C bonds. The aim of this review is to provide a comprehensive survey on the synthesis of propargylamines by the CDC of amines and terminal alkynes from three fronts: (a) transition-metal homogeneous catalysis, (b) transition-metal heterogeneous catalysis and (c) photoredox catalysis. A section dealing with the asymmetric synthesis of chiral propargylamines is also included. Special attention is also devoted to the proposed reaction mechanisms.This work was generously supported by the Spanish Ministerio de Ciencia, Innovación y Universidades (MICIU; grant no. CTQ2017-88171-P), the Generalitat Valenciana (GV; grant no. AICO/2017/007) and the Instituto de Síntesis Orgánica (ISO). I.B. is also grateful to the Spanish MICIU for a Juan de la Cierva-incorporación grant (no. IJCI-2017-33706)

Efficiency of time series homogenization: method comparison with 12 monthly temperature test datasets

The aim of time series homogenization is to remove nonclimatic effects, such as changes in station location, instrumentation, observation practices, and so on, from observed data. Statistical homogenization usually reduces the nonclimatic effects but does not remove them completely. In the Spanish ‘‘MULTITEST’’ project, the efficiencies of automatic homogenization methods were tested on large benchmark datasets of a wide range of statistical properties. In this study, test results for nine versions, based on five homogenization methods—the adapted Caussinus-Mestre algorithm for the homogenization of networks of climatic time series (ACMANT), ‘‘Climatol,’’ multiple analysis of series for homogenization (MASH), the pairwise homogenization algorithm (PHA), and ‘‘RHtests’’—are presented and evaluated. The tests were executed with 12 synthetic/surrogate monthly temperature test datasets containing 100–500 networks with 5–40 time series in each. Residual centered root-mean-square errors and residual trend biases were calculated both for individual station series and for network mean series. The results show that a larger fraction of the nonclimatic biases can be removed from station series than from network-mean series. The largest error reduction is found for the long-term linear trends of individual time series in datasets with a high signal-to-noise ratio (SNR), where the mean residual error is only 14%–36% of the raw data error. When the SNR is low, most of the results still indicate error reductions, although with smaller ratios than for large SNR. In general, ACMANT gave the most accurate homogenization results. In the accuracy of individual time series ACMANT is closely followed by Climatol, and for the accurate calculation of mean climatic trends over large geographical regions both PHA and ACMANT are recommended.This research was funded by the Spanish MULTITESTproject (Ministry of Economics and Competitiveness, CGL2014-52901-P)

East Africa precipitation variability during recent decades

Póster presentado en: 8th Ipwg and 5th Iwssm Joint Workshop celebrado en Bolonia, Italia, del 3 al 6 de octubre de 2016.Estimating space-time variability of precipitation is an important task in East Africa, considering the observed increased frequency of extreme events, drought episodes in particular. These events deeply affect the population with implications on agriculture and consequently food security. Daily accumulated precipitation time series from satellite retrieval algorithms, ARC, CHIRPS, TAMSAT, TMPA-3B42, and CMORPH are exploited to study the spatial and temporal variability of East Africa (EA – 5°S-20°N, 28°E-52°E) precipitation during last decades. The analysis is carried out by computing the time series of the joint CCI/CLIVAR/JCOMM Expert Team on Climate Change Detection and Indices (ETCCDI, http://etccdi.pacificclimate.org/index.shtml), e.g. CDD, CWD, SDII, PRCPTOT, and R1, at the yearly and seasonal scales. The purpose is to identify the occurrence of extreme events (droughts and floods), and extract precipitation spatial patterns of variation by trend analysis (Mann-Kendall technique). Prior to the analysis satellite time series are checked for the possible presence of inhomogeneities due to variations in rain gauge density and/or in the satellite retrieval algorithms

Advances in the homogenization of daily peak wind gusts: an application to the Australian series

Póster presentado en: EGU General Assembly 2018 celebrada del 8 al 13 de abril en Viena, Austria.Daily Peak Wind Gusts (DPWG) time-series are valuable data for evaluation of wind related hazard risk to the population and different economic sectors. Yet wind time-series are prone to be affected by inhomogeneities temporally and spatially (e.g. through change of instruments at a site compared to surrounding sites) that may mislead the studies of their variability and trends. The aim of this work is to present the advances in the homogenization of DPWG by analyzing 548 sites time-series across Australia covering the 1941-2016 time period. Due to the low correlation coefficients between these series, especially in the first decades when the station density is much lower, the average wind speed data from the NCEP/NCAR reanalysis were tried as reference series. However, their lower correlations with the DPWG data suggests avoiding this approach. We proposed a robust monthly homogenization using the R package Climatol, which detected 353 break-points at the monthly scale. Some of them were supported by the history of the stations, but detailed analysis of the metadata of 35 selected stations did not find a good correspondence since many changes do not necessarily produce inhomogeneities. When NCEP/NCAR reanalysis are used as references, more break-points are detected around 2003, but it is not clear whether they are due to a general change of the DPWG algorithm in the observation network or rather an artifact due to inhomogeneities in the reanalysis series. The monthly dates of the detected break-points were used in a new application of the Climatol package to adjust the series at daily basis, yielding a homogenized and filled DPWG database for assessing the variability of extreme wind events. Resultant trends of the homogenized DPWG series showed the benefits of the homogenization in the form a much lower dispersion of their values.This work has been also supported by the Project “Detection and attribution of changes in extreme wind gusts ove rland” (2017-03780) funded by the Swedish Research Council, and the MULTITEST (Multiple verification of automatic software homogenizing monthly temperatura and precipitation series; CGL2014-52901-P) Project ,funded b ythe Spanish Ministry of Economy and Competitivity